How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Gary Your Own Question
Gary
Gary, Buick Technician
Category: Buick
Satisfied Customers: 16402
Experience:  15 years master GM tech and mater ASE tech
19513769
Type Your Buick Question Here...
Gary is online now
A new question is answered every 9 seconds

Code p0303 cylinder misfire detected

Customer Question

Code p0303 cylinder misfire detected
Submitted: 1 year ago.
Category: Buick
Expert:  Gary replied 1 year ago.

can you tell me the year ?

has anything been done yet to correct this issue ?

was anything done to the car that now you have this problem ?

Customer: replied 1 year ago.

2003 buick

I didn't do anything yet. I have indicated changing the plug, and changing the problem cylinder plug wire with the number one wire entirely. Nothing changed. I gave the freeze frame information to you

Expert:  Gary replied 1 year ago.

so changing the wire and plug did not move the problem or fix it yet

can you feel it miss ?

Customer: replied 1 year ago.

Yes. Rythmatic miss at idle

Expert:  Gary replied 1 year ago.

ok off idle will it miss ?

Customer: replied 1 year ago.

Not off idle.

Expert:  Gary replied 1 year ago.

99 % of these that will miss at idle and not off idle are caused by vacuum leaks from the injector lower o-ring or the upper intake manifold gasket or the upper intake manifold itself cracked or the fuel injector itself

if you confirm NO vacuum leaks and show visual spark at idle and the compression matches the other cylinders on that bank then the only thing left would be the injector itself

as if that injector was NOT being told to fire it would miss all the time at idle and off idle

if you have any questions please ask as i do not get credit for my work until you rate us here at Justanswer

Customer: replied 1 year ago.

I took the number 3 injector out. I have the means to click it open. I blew through it and barely any air came out and a little gasoline drop came out.

Expert:  Gary replied 1 year ago.

you can either swap it with the 1 or 5 injector and see if the misfire moves or replace it since its out if it just was dripping

you can always get me back through this post for FREE with any follow up with this question even after you rate us here as i do not get credit for my work until you rate us here at Justanswer

Customer: replied 1 year ago.

Can some carb cleaner clean it out?

Expert:  Gary replied 1 year ago.

no these can not be cleaned out

Customer: replied 1 year ago.

I took the fuel injector wire connector loose and ran the engine like that and I didn't notice that much difference, but of course if you rev the engine ... you know.

Expert:  Gary replied 1 year ago.

swapping # ***** injector physically with the # ***** injector will the misfire move to cylinder # ***** ?

Customer: replied 1 year ago.

If the stays on the same cylinder after swapping injectors what then?

Expert:  Gary replied 1 year ago.

ok then can you do a compression test and see if the PSI is the same as 1 and 5 ?

Customer: replied 1 year ago.

I found a fuel injector connector with a broken terminal on number one. I have to go to the salvage yard to get another one. Not only do I have a plugged fuel injector, but now another fuel injector isn't functioning.

Stupid question: is driving the car in this state doing more damage ?

Expert:  Gary replied 1 year ago.

the only thing it can do is damage the cat converter with a misfire but that is usually from the fuel pooling up unburnt but since the issue is a lack of fuel it should not hurt anything

you can always get me back through this post for FREE with any follow up with this question even after you rate us here as i do not get credit for my work until you rate us here at Justanswer

Customer: replied 1 year ago.

I was able to rig the connections on cylinder one. I drove the car with only one inoperative fuel injector. Last night I did switch the injectors like you advised. I got another injector too. Still, after all this, cylinder 3. This event takes place at idle once again.

Cylinder 3 misfire p0303. I looked at the connector on cylinder 3 again. Flush with the connector bottom the wire was perforated. Would that cause what I'm going through now?

Expert:  Gary replied 1 year ago.

does # ***** show an injector pulse at it at idle using an injector noide light or a test light to watch the bulb blink at idle ?

Customer: replied 1 year ago.

I dont know how to do that

Expert:  Gary replied 1 year ago.

if you have a test light with the key ON one terminal in the injector connector should show 12 volts if so then connect your test light clip to the battery ground and when the car is at idle does the other terminal in the connector blink your test light bulb ?

Customer: replied 1 year ago.

Please gimme some time

Expert:  Gary replied 1 year ago.

ok